 | |
| Names | |
|---|---|
| IUPAC names | |
| Other names Silver fulminate Silver(I) fulminate Argentous fulminate | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider | |
| UNII | |
| |
| |
| Properties | |
| AgCNO | |
| Molar mass | 149.885 g/mol |
| Density | 3.938 g/cm3 |
| Explosive data | |
| Shock sensitivity | Extremely high |
| Friction sensitivity | Extremely high |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Sensitive high explosive |
| NFPA 704 (fire diamond) | |
| 170 °C (338 °F; 443 K) | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Silver fulminate (AgCNO) is the highly explosivesilversalt offulminic acid.
Silver fulminate is aprimary explosive, but has limited use as such due to its extreme sensitivity to impact, heat, pressure, and electricity. The compound becomes progressively sensitive as it is aggregated, even in small amounts; the touch of a fallingfeather, the impact of a singlewater droplet, or a smallstatic discharge are all capable of explosively detonating an unconfined pile of silver fulminate no larger than adime and no heavier than a fewmilligrams. Aggregating larger quantities is impossible, due to the compound's tendency to self-detonate under its own weight.
Silver fulminate was first prepared in 1800 byEdward Charles Howard in his research project to prepare a large variety offulminates. Along withmercury fulminate, it is the only fulminate stable enough for commercial use.Detonators using silver fulminate were used to initiatepicric acid in 1885, but since have been used only by theItalian Navy.[3] The current commercial use has been in producing non-damaging novelty noisemakers as children's toys.
Silver fulminate occurs in twopolymorphic forms, anorthorhombic one and a trigonal one with arhombohedral lattice.[4] The trigonal polymorph consists of cyclic hexamers, (AgCNO)6.[5]
Fulminates are toxic, about the same ascyanides.[3] When pure, silver fulminate is chemically stable, not decomposing after years of storage. Like many silver salts, it darkens with light exposure. It is slightly soluble in cold water and can be recrystallized using hot water.[3][6] It can also be recrystallized from a 20% solution of ammonium acetate.[3] It is not hygroscopic and can explode when moist or under water; it was reported to remain explosive after 37 years under water.[3] It explodes upon contact with concentratedsulfuric acid orchlorine orbromine, but not when contactingiodine.[3] It is insoluble innitric acid, but dissolves inammonia, alkalichlorides, alkalicyanides,aniline,pyridine, andpotassium iodide by forming complexes.[3] Concentratedhydrochloric acid decomposes it non-explosively with a hissing noise;thiosulfate also decomposes it non-explosively, and can be used for disposal.[3]
This compound can be prepared by pouring a solution ofsilver nitrate innitric acid intoethanol, under careful control of the reaction conditions, to avoid an explosion.[7] The reaction is usually done at 80–90 °C; at 30 °C, the precipitate may not form.[3] Only tiny amounts of silver fulminate should be prepared at once, as even the weight of the crystals can cause them to self-detonate.Another way to make silver fulminate is to reactsilver carbonate withammonia in solution.[citation needed]
Silver fulminate also forms when nitrogen oxide gas is passed through a solution of silver nitrate in ethanol.[3]
Silver fulminate can be prepared unintentionally, when an acidic solution ofsilver nitrate comes in contact with alcohol.[7] This is a hazard in some formulations of chemicallysilveringmirrors.
Silver fulminate, often in combination withpotassium chlorate, is used in trick noise-makers known as "throw-downs", "crackers", "snappers", "whippersnappers", "pop-its", or "bang snaps", a popular type of noveltyfirework. They contain approximately 200 milligrams of finegravel coated with a minute quantity (approximately 80 micrograms)[8] of silver fulminate. When thrown against a hard surface, the impact is sufficient to detonate the tiny quantity of explosive, creating a smallsalute from the supersonic detonation. Snaps are designed to be incapable of producing damage (even when detonated against skin) due to the buffering effect provided by the much greater mass of the gravel medium. It is also the chemical found inChristmas crackers[9] having first been used for that purpose byTom Smith in 1860. The chemical is painted on one of two narrow strips of card, with abrasive on the second. When the cracker is pulled, the abrasive detonates the silver fulminate.
A fulminate mixture with 10–20% potassium chlorate is cheaper and morebrisant than the fulminate alone.[3]
Silver fulminate is often confused withsilver nitride,silver azide, orfulminating silver. "Fulminating silver", though always referring to an explosive silver-containing substance, is an ambiguous term. While it may be asynonym of silver fulminate, it may also refer to the nitride or azide, the decomposition product ofTollen's reagent, or analchemical mixture, which does not contain the fulminate anion.
